Step 1

In a small, dry saucepan over low heat, toast poppy seeds, coriander seeds, cloves, peppercorns, cinnamon, cardamom and bay leaf until they release their aromas. Use a mortar and pestle or spice grinder to process into a rough powder. Add garlic, ginger and salt and grind into a smooth paste. In a small bowl, mix with yogurt.

Step 2

Prick deep holes all over the lamb, or make gashes with a knife, then rub marinade all over meat and transfer to a roasting pan. Refrigerate for at least 2 hours, or as long as overnight.

Step 3

Heat oven to 350 degrees. In a saucepan over medium to low heat, heat butter and sauté chopped onion until light golden. Set aside.

Step 4

Add 1 cup water to the roasting pan with the lamb, cover tightly with foil and bake for 45 minutes. Gently flip the lamb over and bake for another 45 minutes. Flip the lamb again, pour the onions and clarified butter over the lamb and roast uncovered for about 1 hour, until the meat is tender, cooked through and lightly browned on the surface. If the pan starts to get dry at any time, add 1/2 cup water to it. When ready to serve, garnish the lamb with the fried onions, cilantro and lemon slices.